DE2557262A1 - PISTONS AND CYLINDERS FOR TWO-STROKE COMBUSTION MACHINES - Google Patents

Description

KARL SCHMIDT GMBH 6 Ffm., December 17, 1975

7107 Neckarsulm DrQ / GKp

Christian-Schmidt-Strasse 8/12

Prov. No. 7807 KS '3

Pistons and cylinders for two-stroke internal combustion engines

Pistons and cylinders for second-component Br ermkraf machines with pre-compression of the fuel-air mixture in the crankcase and overflow of the fuel-air mixture through overflow channels in the cylinder wall into the combustion chamber under control of the piston movement _r with the piston skirt having window-like openings in the Area of the end faces of the piston pin, which is mounted in the pin bosses of the bearing blocks hanging on the piston crown, which in the area of the bottom dead center of the piston cover the openings of the overflow ducts in such a way that the pre-compressed fuel-air Gern passes through the interior of the piston _f through the window-like openings in the piston skirt and the overflow channels.

It is known (DT-PS 571 548j FR-PS 1 092 282) _f to provide arrangements on the piston itself which allow the gases to flow along the piston _c By these arrangements it is possible ^ to provide a long piston skirt with the known advantages even in relatively short-stroke internal combustion engines _c With these known pistons

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groove-like depressions are provided along the surface lines going through the ends of the piston pin from the free end of the piston skirt to below the ring zone «

It is also known (DT-PS 692 211), in the piston skirt one or more window-like openings in the sections between the piston pin bearings provide so that the mixture through the interior of the Piston poured

Although these known arrangements provide the one hand a relatively short overflow path that is not as _s must at conventional piston amount to the whole height of the piston, but only the height of the annular zone on the other hand, however, result from the cooling effect of the mixture flow and the great heat absorption of the piston, in particular at fast rotating internal combustion engines with high compression, thermal stresses in the piston.

To avoid this, consider the last one known arrangement provided a Zwangsstromungsweg along the piston head by appropriate partitions. As a result, the thermal permeations are avoided and the piston is cooled, but on the other hand the flow resistance is considerably increased and thereby the Delay time extended. In addition, it is particularly with small pistons with high power and thus accordingly extensive piston pin bearing limits the possible cross-section.

To eliminate these disadvantages, a piston for two-stroke internal combustion engines with pre-compression of the Fuel-air mixture in the crankcase and transfer

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this mixture is provided through the overflow channel arranged in the cylinder wall under control by the piston movement, the piston being window-like Has openings, which in the area of the bottom dead center with the overflow channels in the cylinder wall coincide in such a way that the compressed fuel-air mixture through the interior of the piston on the piston pin over, through the window-like openings in the piston skirt and the overflow channels to the flushing slots » flows at the end of these overflow channels. With these pistons, the piston pin is open on the piston crown. suspended bearing blocks and the window-like openings are opposite the end faces of the piston pin attached * (DT-AS 14 76 085)

A major disadvantage of this piston is that the interior of the piston is not sufficiently covered by the gas exchange, which leads to local overheating and the associated consequences. The cylinder has a compact combustion bowl _t in its head which, depending on the arrangement of the spark plug _{s, is} often not or only incompletely flushed by the fuel-air mixture flowing into the combustion chamber, so that here too no or only an incomplete gas exchange can take place and poor starting behavior due to the burnt residual gases upstream of the spark plug, especially when the machines are still warm, is the result. For this reason, not only the performance is impaired, but also the composition of the exhaust gases is negatively influenced,

The object of the present invention is therefore to provide the piston and cylinder in one described at the outset

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To design the two-stroke internal combustion engine. " that an improved gas exchange _f . a complete combustion of the fuel-air mixture and an improvement in the starting behavior and thus a satisfactory performance and composition of the exhaust gases can be achieved.

The solution to this problem is that the size of the window-like openings arranged in the piston shaft corresponds approximately to the size of the openings of the overflow channels opposite at the bottom dead center of the piston and the distance between the flow-favorable shape and the lower frame of the window like openings connected BoI Kennaben as small as possible and the combustion bowl is largely arranged in the piston crown.

By combining these measures a large axial flow cross section is füi'- achieved in the piston inside the overflowing fuel-air mixture, whereby the volumetric efficiency is significantly improved "The overflowing fuel" air Qomi beautiful sweeps not only all areas of KoXbeninneren and thereby effects A cooling system _f Bondern also lubricates the bearing of the piston pin * In addition, the combustion chamber roughness arranged in the piston crown forms a compact combustion chamber that completely or for the most part replaces the poorly flushable combustion chamber bowl located in the cast-on cylinder head according to the state of the art * technology, whereby improved flushing is achieved which prevents the piston crown from becoming too bright in relatively narrow areas.

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Another embodiment of the invention is arranged in the cylinder transfer ducts as for For-di! The _f that the form in the combustion chamber entering fuel-air mixture flows with their inner sides in each case a tangent to the edge regions of the combustion chamber recess in the piston crown ■ located " in this way, they are d in their effect on postponing €; not impaired r exhaust gases Further, the spark plug is located by aie £ he jridungsgemäße arrangement of 35rennrauinrmi.'lde, in Sti'ömungsbereich of the incoming fuel-air mixture, which not only the service life of the spark plug is improved, but also fresh fuel gas is always stored in front of the spark plug, even if the combustion bowl located in the piston crown should not be completely flushed through achieved the internal combustion engine.

In accordance with the preferred embodiment of the invention, the Brenni'aummulde is wholly or at least 60% in the piston head arm shows _eight-f wherein the other part of the combustion chamber recess in the form of a comparatively flat in the latter case. The recess is located in the cylinder head ».

The outer distance zvö see the bolt eyes is expediently chosen so that it is less than 40 % of the piston diameter «.

The invention is illustrated by way of example in the drawing explained in more detail below

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It show * * ^%

Fig. Λ a longitudinal section through the cylinder perpendicular to the bolt plane and a side view of the piston in the bottom dead center position on the face of the piston pin.

Fig. 2 shows a longitudinal section through the. Pistons located in the bottom dead center position and the cylinder along the plane of the piston pin.

3 shows a cross section along the section line 1-1 of Fig. 2.

In the cylinder 1, which is provided with cooling fins, the piston 2 is in its bottom dead center position. On the bottom 3 of the piston 2, two bearing blocks k are attached, in the hubs 5 of which the piston pin 6 is mounted Openings 8, the size of which corresponds to the size of the openings in the overflow channels 9 _f 10 for the fuel-air mixture in the combustion chamber 11 and which coincide with each other in the bottom dead center position of the piston 2 _r attached perpendicular to the plane of the piston pin 6 are the intake openings 12 For the fuel-air mixture and the outlet openings 13 for the exhaust gases, approx. 65 % of the combustion chamber bowl 14 is located in the piston crown 3 , while the remaining part 15 is a flat bowl in the cylinder head into which the spark plug 16 protrudes . In Figc. 3, the lateral delimitation lines of the combustion gases entering the combustion chamber 11 via the overflow duct are drawn in dash-dotted lines.

Claims

709 8 2 6/04 53

Claims (5)

PATENT CLAIMS 1) piston and. Cylinder for two-stroke Brennkra.ftmascbl.J3.en, κ ^ / with pre-compression of the fuel-air mixture in the crankcase and overflow of the fuel-air mixture through overflow channels arranged in the cylinder wall into the combustion chamber under control of the piston movement j where the Piston shaft has window-like openings in the area of the end faces of the piston pin, which is mounted in the pin bosses of bearing blocks hanging on the piston head, which in the area of the bottom dead center of the piston coincide with the openings of the overflow channels in such a way that the pre-compressed fuel Air mixture flows through the interior of the piston, through the window-like openings of the piston skirt and the overflow channels into the combustion chamber provided with combustion bowls, characterized in that the size of the window-like openings (8) made in the piston skirt (7) is approximately the size of the lower dead center position opposite openings of the overflow channels (9, 10) corresponds to u nd the distance between the pin bosses, which have a flow-favorable shape and connected to the lower frame of the window-like openings, is as small as possible and the combustion bowl (14) is largely arranged in the piston head (3). 2) Two-stroke internal combustion engine according to claim 1 » gekennzeiohnet that the combustion bowl (14) is arranged entirely in the piston head (3). 3) Two-stroke internal combustion engine according to claim 1, characterized in that the combustion bowl (14) is arranged to at least 60 % in the piston head and the other part (15) in the form of a comparatively flat bowl in the cylinder head. 709826/0453 " ⁸ " QRiGJNAL INSPECTED 25572G2 ■% ■ 4) Two-stroke internal combustion engine according to claims 1 Ms 3 _S dad urch g ekmarks that the outer distance between the pin bosses (5) is less than 40 % of the basket diameter. 5) Two-stroke internal combustion engine according to claims 1 "to 4, characterized _s that the outlet openings of the transfer channels are (9 10) designed? In the combustion chamber (11) so j that the inner boundary of the combustion chamber entering Brennstof t" Lu £ t-mixture "currents j s eweil a tangent to the edge region of the combustion bowl (14) located in the piston head (3) form" 709826/04 B3